1. Field of the Invention
This invention relates generally to rapidly solidified iron-aluminum-copper alloys obtained by adding small amounts of boron. This invention also relates to the preparation of these materials in the form of rapidly solidified powder and consolidation of these powders (or, alternatively, the rapidly solidified ribbon-like material) into bulk parts which are suitably heat treated to have desirable properties. This invention also relates to the preferred iron rich metal alloy compositions made by this method.
2. Description of the Prior Art
Rapid solidification processing (RSP) techniques offer outstanding prospects of new cost effective engineering materials with superior porperties [see Proc. Int. Conf. on Rapid Solidification Processing; Reston, VA, 1980; Published by Claitors Publishing Division, Baton Rouge, LA]. Metallic glasses, microcrystalline alloys, supersaturated solid solutions and ultrafine grained alloys with highly refined microstructures, in each case, often having complete chemical homogeneity are some of the products that can be made by utilizing RSP. [See Rapidly Quenched Metals, 3rd Int. Conf. Vol. 1 and 2, Cantor Ed; The Metals Society, London, 1978].
Several techniques are well established in the state of art to economically fabricate rapidly solidified alloys (at cooling rates of .about.10.sup.5.degree. to 10.sup.7 .degree. C./sec) as ribbons, filaments, wires, flakes or powders in large quantities. One well known example is melt spin chill casting whereby the metal is spread as a thin layer on a conductive metallic substrate moving at high speed to form rapidly solidified ribbon. [See Proc. Int. Conf. on Rapid Solidification Processing, Reston, VA, 1977].
The current technological interest in materials produced by RSP, especially when followed by consolidation into bulk parts, may be traced in part to the problems associated with micro and macro segregation and undesirable massive grain boundary eutetic phases that occur in highly alloyed materials during conventional slow cooling processes (i.e.) ingot or mold casting. RSP removes macrosegregation altogether and significantly reduces spacing over which microsegregation occurs, if it occurs at all.
The design of alloys made by conventional slow cooling process is largely influenced by the corresponding equilibrium phase diagrams which indicate the existence and coexistence of the phases present in thermodynamic equilibrium. Alloys prepared by such processes are in or at least near equilibrium. The advent of rapid quenching from the melt has enabled material scientists to stray further from the state of equilibrium and has greatly widened the range of new alloys with unique structures and properties available for technological applications.
Commercial iron base alloys containing chromium and/or nickel find extensive use in corrosion and oxidation resistant applications. There have been limited efforts as reported in the prior art involving use of rapid solidification processing techniques to synthesise new oxidation and corrosion resistant iron base alloys which do not contain chromium, an element with less abundant natural deposits. A need therefore exists to develop new chromium-free iron base alloys with superior mechanical, oxidation and corrosion resistant properties for numerous industrial applications.